Strange Question I know, but...

This is a weird question I have always wondered about (I hope you understand it!) but is the increase in focal length from say 50mm-150mm equal to when you increase from say 450-550. Its just the numbers on the lens barrel get closer together as you zoom more.

Maybe I'm just going crazy

I'm not sure if this answers your question but in zooms there are groups of elements that move as you zoom in or out. So depending on the particular zoom it may be that a particular group of elements would need to move more as you get wider than when you are at longer focal lengths. I think its even more likely when you are in the part of the zoom range where the lens is going from wide to normal than tele to longer tele.

No, it is not the same. The angle of view is more at wider angles, and that is why the numbers are closer as you zoom more.

Going from 14mm to 16mm is much more than going from 90mm to 100mm for example.

Think of it more as a percentage. Going from 50 to 150 will yield an image size 3 times larger. Going from 400-550 wouldn't even come close to doubling the image size

jra wrote in post #15145315
Think of it more as a percentage. Going from 50 to 150 will yield an image size 3 times larger. Going from 400-550 wouldn't even come close to doubling the image size

Great answer - thanks for that! Now I understand.

The number distance difference is the same and so the focal length distance difference is the same. The field of view ratio difference is what is not the same. That is why a 1mm focal length difference at the wide end (say 10-20mm) but a 1mm difference at 200mm means almost nothing. (That last sentence applies for normal camera length viewing distances.)

A $100.00 is a $100.00. If you add it to $50.00 it is quite an increase. But if you add it to $800.00 it is not so much. Even though it is still a $100.00. Oh yea we were talking about millimeters.

Mike

Heycoop Photography wrote in post #15145194
This is a weird question I have always wondered about (I hope you understand it!) but is the increase in focal length from say 50mm-150mm equal to when you increase from say 450-550. Its just the numbers on the lens barrel get closer together as you zoom more.

Maybe I'm just going crazy

An increase from 50 to 150mm is 300% of the starting point.
And increase from 450 to 500mm is only 111% of the starting point.

A 111% increase from 50mm is going to 55.5mm!

The effect of FL changes in millimeters are relative to a starting point.